1. Field of the Invention
The present invention relates to Fibre Channel networks, and more particularly to a transparent Fibre Channel switch that facilities communication in a Fibre Channel network that includes at least a proprietary Fibre Channel fabric switch.
2. Background of the Invention
Fibre Channel is a set of American National Standard Institute (ANSI) standards, which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre Channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre Channel supports three different topologies: point-to-point, arbitrated loop and Fibre Channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop. The Fibre Channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The Fibre Channel fabric topology allows several media types to be interconnected.
In Fibre Channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at high speed with low latency, performing only simple error detection in hardware.
Fibre Channel fabric devices include a node port or “N_Port” that manages fabric connections. The N_port establishes a connection to a fabric element (e.g., a switch) having a fabric port or F_port. Fabric elements include the intelligence to handle routing, error detection, recovery, and similar management functions.
A Fibre Channel switch is a multi-port device where each port manages a simple point-to-point connection between itself and its attached system. Each port can be attached to a server, peripheral, I/O subsystem, bridge, hub, router, or even another switch. A switch receives messages from one port and automatically routes it to another port. Multiple calls or data transfers happen concurrently through the multi-port Fibre Channel switch.
Fibre Channel switches use memory buffers to hold frames received and sent across a network. Associated with these buffers are credits, which are the number of frames that a buffer can hold per fabric port.
Storage area networks (“SANs”) are commonly used where plural memory storage devices are made available to various host computing systems. Data in a SAN is typically moved from plural host systems (that include computer systems, servers etc.) to a storage system through various controllers/adapters. The Fibre Channel standard is commonly used in SANs today.
FIG. 1A shows an example of a Fibre Channel network. In FIG. 1A, host system 10 is coupled to a standard fabric switch 13. Host system 10 (and/or 10A) typically includes several functional components. These components may include a central processing unit (CPU), main memory, input/output (“I/O”) devices (not shown), read only memory, and streaming storage devices (for example, tape drives).
Host systems (for example, 10 and 10A) often communicate with storage systems (for example, devices 15 and 27) via a host bus adapter (“HBA”, may also be referred to as a “controller” and/or “adapter”) using an interface, for example, a “PCI” or PCI-X bus interface.
FIG. 1A shows four HBAs, 11, 12, 20 and 22. HBA 11 is coupled to switch 13 via port 17, HBA 12 is coupled via port 18, HBA 20 is coupled via port 19 and HBA 22 is coupled via port 21.
Fabric switch 13 is coupled to a proprietary Fibre Channel fabric switch 14 (may also be referred to as “Proprietary Switch 14” or “switch 14”) via ports 23 and 16. Fabric switch 13 is also coupled to another proprietary Fibre Channel fabric 26 via ports 24 and 25. Proprietary Switch 14 is coupled to device 15 that may be a storage sub-system, while proprietary fabric switch 26 (may also be referred to as “proprietary switch 26” or “switch 26”) is coupled to device 27 which may also be a storage sub-system.
Devices 15 and 27 may be coupled using the Small Computer Systems Interface (“SCSI”) protocol and use the SCSI Fibre Channel Protocol (“SCSI FCP”) to communicate with other devices/systems. Both the SCSI and SCSI_FCP standard protocols are incorporated herein by reference in their entirety. SCSI FCP is a mapping protocol for applying SCSI command set to Fibre Channel.
Although Fibre Channel is an industry standard, proprietary switches, for example, 14 and 26 are quite common. Such switches often use confidential internal switching technology that allows a host system to communicate with a target device and vice-versa. Often a Fibre Channel network has more than one proprietary switching technology. Brocade Communications Inc® and McData Corporation® are two such corporations that provide such proprietary switching technology.
Proprietary switches have shortcomings. For example, when a proprietary switch (for example, 14) locates/communicates with a non-proprietary switch (for example, fabric switch 13) there is a loss of functionality. This forces SAN builders to use the proprietary switching technology. This loss of functionality becomes sever in mixed vendor environment. For example, in FIG. 1A, use of switch 13 will result in loss of functionality with respect to both switches 14 and 26.
Although standardization is the future of Fibre Channel networks, mixed vendor configurations are a commercial reality. Therefore, there is a need for a Fibre Channel switch that will allow host systems and devices to communicate in a configuration with mixed vendor/proprietary switching technology without any loss of functionality.